Directional Emission, Increased Free Spectral Range, and Mode $Q$-Factors in 2-D Wavelength-Scale Optical Microcavity Structures

Abstract

Achieving single-mode operation and highly directional (preferably unidirectional) in-plane light output from whispering-gallery (WG) mode semiconductor microdisk resonators without seriously degrading the mode Q-factor challenges designers of low-threshold microlasers. To address this problem, basic design rules to tune the spectral and emission characteristics of micro-scale optical cavity structures with nanoscale features by tailoring their geometry are formulated and discussed in this paper. The validity and usefulness of these rules is demonstrated by reviewing a number of previously studied cavity shapes with global and local deformations. The rules provide leads to novel improved WG-mode cavity designs, two of which are presented: a cross-shaped photonic molecule with introduced asymmetry and a photonic-crystal-assisted microdisk resonator. Both these designs yield degenerate mode splitting, as well as Qfactor enhancement and directional light output of one of the split modes.

Heat meets light on the nanoscale

“…Local perturbations in symmetrical emitters can help to match the momentum of the high-k trapped modes to the low-k propagating modes in free space, thus facilitating far-field extraction of the optical energy. In particular, Boriskina has previously predicted that localized indentations can be used to generate highly directional light emission from WGM microcavities [148,149], which has been subsequently proven experimentally [150].…”

Resonant lenses as building blocks for advanced narrow-band integrated receivers

“…When excited, WG resonances cause increase of the side-lobe level (SLL) -see Fig. 1 -that is explained by the omnidirectional pattern of the corresponding natural modes [13]. Thus in most scenarios (related to lens antennas) excitation of WG resonances is an unwanted phenomenon.…”

“…Whereas the "cut top" of the lens (see Fig. 5a) helps transform the symmetrical multi-beam radiation pattern of the WG mode to a nonsymmetrical directive one (as shown in [13], a local distortion on the surface of a circular WGM resonator gives rise to a directive radiation in the direction opposite to the distortion position). The latter explains the role of the PEC ground plane which is needed to "mirror" the radiation related to the distorted WGM mode and thus to contribute in the main beam formation.…”

Combining Different in-Plane Photonic Wire Lasers and Coupling the Resulting Field Into a Single-Mode Waveguide

“…Nowadays, there are different physical phenomena that can be used to confine light at the micrometer/sub-micrometer scale such as the photonic bandgap effect [1][2][3][4][5][6][7], total internal reflection [8][9][10][11] and plasmonic propagation [12][13][14][15][16][17]. An example of compact device based upon total internal reflection is the photonic wire [18]: they have widths in the range of a few hundreds of nanometers and light is confined laterally by total internal reflection at the boundaries between the core and low refractive-index air layers.…”